This application is based on and claims priority to Japanese Patent Application No. 2001-054767, filed Feb. 28, 2001, the entire contents of which are hereby expressly incorporated by reference.
1. Field of the Invention
The present invention relates to cooling systems for marine engines. More specifically, the present invention relates to an improved cooling water jacket arrangement within a lubrication oil reservoir.
2. Description of Related Art
Personal watercraft have become very popular in recent years. This type of watercraft is quite sporting in nature and carries one or more riders. A relatively small hull of the personal watercraft defines a rider""s area above an engine compartment. An internal combustion engine powers a jet propulsion unit which propels the watercraft. The engine lies within the engine compartment in front of a tunnel formed on an underside of the hull. The jet propulsion unit, which includes an impeller, is placed within the tunnel. The impeller has an impeller shaft driven by the engine. The impeller shaft usually extends between the engine and the jet propulsion device through a bulkhead of the hull tunnel.
Four-stroke engines include lubrication systems arranged to supply lubrication oil to various portions of their engines, such as the crankshaft chamber and camshaft chamber. Desirably, a volume of lubrication oil is provided within a reservoir to be available for supply to the engine. The lubrication oil is permitted to cool upon being returned to the reservoir before again being supplied to the engine.
Such watercraft designs also typically include a cooling system arranged to supply a cooling fluid, such as cooling water, to various portions of the engine, such as the cylinder block and exhaust system, through cooling water passages. Cooling water additionally is supplied to a water jacket formed within a wall of the lubrication oil reservoir, to further cool the oil therein. Commonly, a single water jacket is provided which surrounds a large portion of the reservoir, to cool the lubrication oil.
One aspect of the present invention involves the discovery that a single oil reservoir water jacket provides inadequate cooling of lubrication oil, especially in connection with high-revving four stroke engines. With a reservoir arrangement having a single water jacket, the velocity of the cooling water may be dramatically reduced as it enters the water jacket due to the large increase in volume from the cooling water supply passage to the water jacket. As a result, the cooling effect provided by the cooling water is reduced in comparison to the cooling effect if the cooling water velocity was maintained. Additionally, the flow pattern of the cooling water within a single, large water jacket of the reservoir is likely to be inconsistent, resulting in some portions of the reservoir being cooled more quickly than other portions.
Another aspect of the present invention involves a small watercraft comprising a hull defining an engine compartment. An internal combustion engine is disposed in the engine compartment. A lubrication system is arranged to supply lubrication oil to the engine and includes a reservoir at least partially defining a space for holding lubrication oil therein. A first cover member is connected to an outer surface of the reservoir to define a first cooling jacket portion therebetween and a second cover member is connected to an outer surface of the reservoir opposite the first cover member. The second cover member and the reservoir define a second cooling jacket portion therebetween. A first transverse passage and a second transverse passage connect the first and second cooling jacket portions. The first and second cooling jacket portions and the first and second transverse passages at least partially define a cooling jacket of the reservoir. An inlet and an outlet are provided in fluid communication with the cooling jacket. A cooling system of the watercraft is arranged to supply cooling fluid to the inlet and receive cooling fluid from the outlet. The cooling jacket includes a plurality of horizontal passages and is configured to guide a flow of cooling fluid between the plurality of horizontal passages.
An additional aspect of the present invention involves a marine engine comprising an engine body defining at least one combustion chamber therein. The engine body includes a cylinder head portion having a plurality of intake valves and a plurality of exhaust valves permitting selective communication with the combustion chamber. The cylinder head portion supports a cam shaft configured to actuate the intake and exhaust valves. A lubrication system is arranged to supply lubrication oil to a portion of the engine body and includes a reservoir at least partially defining a space therein for holding lubrication oil. The reservoir includes a cooling jacket in thermal communication with the space within the reservoir and an inlet and an outlet are provided in fluid communication with the cooling jacket. A cooling system is arranged to supply a flow of cooling fluid to the cooling jacket through the inlet and receive cooling fluid from the outlet. The cooling jacket includes a plurality of distinct horizontal passages. The horizontal passages being in fluid communication with one another. The cooling jacket is arranged such that the flow of cooling fluid passes in series through at least a portion of the horizontal passages.